The above workpiece conveyance device is known in automobile assembly lines, for example. In automobile assembly lines, the first conveying path is used as a trim line or final line where work with respect to a relatively low region of the periphery of an automobile body having been supported on a workpiece conveying traveling body is performed, by driving the workpiece conveying traveling body to travel in a longitudinal orientation parallel to the front-rear direction of the supported automobile body. The second conveying path is used as a chassis line where work of assembling an engine or an axle unit from beneath the automobile body having been supported on the workpiece conveying traveling body is performed, by driving the workpiece conveying traveling body to travel in a transverse orientation orthogonal to the front-rear direction of the supported automobile body. As the workpiece conveying traveling body usable in such workpiece conveyance device, there have been known a variable-length conveying carriage provided with auxiliary stands before and after a workpiece support carriage which slidably move in and out as described in Patent Document 1 and a variable-length conveying carriage pivotally supporting auxiliary stands before and after a workpiece support carriage so as to rise and fall.    Patent Document 1: Japanese Published Unexamined Patent Application No. H04-362459
However, in the conventional and known variable-length workpiece conveying traveling body as described above, not only does the structure of the workpiece conveying traveling body required in large numbers of the entire equipment become complicated thereby leading to high cost as the entire equipment, but also the size of the auxiliary stands is inevitably restricted since the auxiliary stands are accommodated in a carriage main body or switched into a hanging posture, so that the effectiveness of the auxiliary stands is reduced. Further, a means for taking out and in the auxiliary stands with respect to the carriage main body and control for automatically operating the means become necessary at a branching point from the first conveying path to the second conveying path or at a meeting point from the second conveying path to the first conveying path. In this respect, cost of the entire equipment also becomes significantly higher. In order to solve such problems, proposed is conveyance device in which the workpiece conveying traveling body is composed of a workpiece support carriage which supports a longitudinal central portion of an automobile body whose longitudinal direction is parallel to the first conveying path and front and rear two auxiliary carriages which adjoin the front and rear in the traveling direction of the first conveying path of the workpiece support carriage and are positioned below both longitudinal end portions of the automobile body, and the workpiece support carriage and the two auxiliary carriages are driven to travel linearly and integrally on the first conveying path, and only the workpiece support carriage having been laterally extracted from between the front and rear two auxiliary carriages is driven to travel perpendicularly and horizontally on the second conveying path.
In the new workpiece conveyance device in which the workpiece conveying traveling body is composed of a workpiece support carriage and two auxiliary carriages arranged before and after the workpiece support carriage as described above, also, on the first conveying path, the automobile body needs to be supported at a low position where a variety of works with respect to the periphery of the automobile body (the workpiece) can be performed easily, and on the second conveying path, the automobile body needs to be supported at a position high enough for a worker to enter under the automobile body. In order to solve such problems, it is conceived in the above proposal that a workpiece support means provided on the workpiece support carriage is configured to be able to support the automobile body at any height from a high position to a low position.